1. Field of the Invention
The present invention relates to liquid storage unit and a liquid ejecting apparatus mounting the liquid storage unit thereon.
2. Related Art
Conventionally, a liquid ejecting apparatus for injecting a droplet from the nozzle of a liquid ejection head includes an ink jet printer. Some ink jet printers include an ink supply system of an off carriage type for mounting an ink cartage in a place other than a carriage. The case in which the ink supply system of the off carriage type is provided includes the case in which an ink cartridge having a large capacity is provided for large printing and the case in which the ink cartridge is not mounted but the size of a carriage is reduced and the size and thickness of the ink jet printer is decreased.
In the ink supply system of the off carriage type, for example, the ink cartridge is provided on a body side. An ink is supplied from the ink cartridge to a subtank mounted on the carriage through a supply tube. On the other hand, there is a problem in that the dynamic pressure of the ink in the supply tube is raised because of an increase in the flow of the ink due to an increase in the speed and fineness of the printing of a printer, resulting in the insufficiency of the amount of the ink supplied to the subtank.
In order to solve the problem, there has been proposed an ink cartridge for accommodating a bag-shaped ink pack in the case of the ink cartridge and introducing air between the case and the ink pack, thereby pressurizing the ink pack to forcibly lead out an ink (for example, see JP-A-2001-212973).
In the ink cartridge for accommodating the bag-shaped ink pack in the case, however, it is necessary to raise an air pressure between the case and the ink pack. For this reason, the opening portion of the case for attaching the ink pack is to be sealed in an airtight state as shown in FIG. 10. In an ink cartridge 51, a plug member 55 sealing the opening portion of an ink pack 54 is protruded from an opening portion 53 formed on a case 52 toward an outside. In this state, an O-ring 56 is attached to the opening portion 53, and furthermore, an engaging member 57 is pushed in from the outside of the case 52. Consequently, the plug member 55 is fixed to the opening portion 53 in the airtight state.
In the ink cartridge for accommodating the bag-shaped ink pack in the case, accordingly, a seal member for enhancing a sealing property is required and the structure of the seal member is complicated. Accordingly a cost is increased or the size of an apparatus is increased in some cases.
To cope with the above problems, there have been proposed an ink cartridge (for example, JP S59-209878A) in which a bag member provided with a flexible film covers a recessed face of the cartridge body so that an ink is filled in a space formed between the bag member and the recessed face. A rigid lid having recess corresponding to the bag member filled with the ink is attached on the cartridge body. The bag member is pressurized by providing air between the bag member and the lid so that the ink is led out from the cartridge.
Since any ink pack is not housed, no sealing member for ink pack is provided in the cartridge. Therefore, such the ink cartridge can be provided with a simple structure in small size at low cost.
Meanwhile, even in the cartridge as disclosed in JP S59-209878A, it is important to keep sufficient deaeration degree of the ink for maintaining the quality of ink. However, in the ink cartridge of JP S59-209878A, the space in which the ink is filled is formed by the flexible film on one side face and the rigid main body on the other side faces. The main body of the cartridge is usually made of a plastic resin with a low gas barrier property. Therefore, even if only one side face is covered with the film with high gas barrier property, the total degree of deaeration of the ink filled in the space does not reach sufficiently high since a large portion of the surface of the space is defined by the main body
Further, in JP S59-209878A, a space into which air is introduced is formed by fixing the rigid lid onto the rigid cartridge body. Accordingly, for fixing the lid onto the main body, it is necessary to use a simple manufacturing device and to avoid generation of foreign substances by operation as much as possible.
The invention relates to a liquid storage unit which is available by a simple manufacturing device, avoiding generation of foreign substances, and a liquid ejection apparatus in which the liquid storage unit is mounted.